The present invention concerns, in the press section of a paper machine, in particular in a so-called closed-conduction press section, a procedure for changing such a felt of which the normal run passes to a substantial part in spaces below floor level, said press section having its lower roll and the potential guide rolls of the felt to be changed which are located adjacent thereto, rotatably carried by one or several cantilever beams.
Furthermore, the invention concerns a means intended for implementing the procedure of the invention and which is applied in connection with the press section, preferably a so-called closed conduction press section, of a paper machine, and said press section comprising a cantilevered beam, in connection of which have been rotatably carried the lower roll of the press and potential felt guide rolls in its vicinity, and one end of said cantilevered beam being supported by one or several inserts which can be taken out for the lower changing operation.
Recently, press fabrics made of synthetic plastic materials have come into common use in paper machine press sections, replacing the textile fabrics which were commonly used before. However, the introduction of these new fabric types has introduced problems associated with the changing of these fabrics. As known in the art, of course, textile fabrics were changed, e.g., so that the felt loop is stuffed in horizontal direction to become a kind of bundle and, starting to spread this out from one edge the felt loop is carried in through the gaps at the removed inserts, to be looped around those rolls which the felt loop will in its operation encircle and lap.
In so-called closed press sections, for instance the same applicant's Sym-Press II (Trademark) press section, the changing of synthetic fabrics involves immense problems. With a view to illustrating these problems, the structural design of said Sym-Press II press section shall now be described in its main features. It is well known that the Sym-Press II press section comprises at least three felts (press fabrics, in general): a first felt, e.g. a pick-up felt operating as press felt in the first and second nips of the press section, and a second felt operating as second press felt in the first nip, and this press section comprises a suction roll passed over by the first press felt, e.g. a pick-up felt. In conjunction with this suction roll two press nips are formed, of which the first press nip is two-felted, being defined by this roll together with a recessed surface press roll, and the second presents a single felt and is defined by said roll together with a smooth-surfaced roll, e.g. a stone roll. In conjunction of said stone roll or equivalent has further been provided the third press nip of the press section, which has its third felt (fabric loop). Changing of the upper felts in the Sym-Press press section and of other equivalent closed conduction upper felts, that is of those felts whose run is mainly located above the base floor level of the paper machine, is mainly possible to carry out with the aid of the overhead hoists or cranes in the paper machine hall. By the changing of the lower press felt in the Sym-Press press section has become a particularly refractory problem, i.e., that of the lower felt of the first two-felted nip. This is because said lower felt runs through the basement space of the paper machine hall, where it is not possible, at least not without expensive special arrangements, to use the overhead cranes of the paper machine hall.